A device for producing cryogenic refrigeration of the type for which the present invention is ideally suited is disclosed and claimed in U.S. Pat. No. 3,620,029. Patentee discloses a displacer-expander type refrigerator where the displacer is cycled against a volume of surge fluid driven through an orifice so that external driving means for the displacer are unnecessary. Work is expended by forcing the surge gas through the orifice into a surge volume chamber whereby the heat generated by such action can be removed by suitable heat exchange. The device of U.S. Pat. No. 3,620,029 includes a two ported rotary valve for admitting high pressure fluid to the variable volume chamber or cold end of the refrigerator and exhausting low pressure expanded gas from the refrigerator. The device according to U.S. Pat. No. 3,620,029 may have more than one stage and most current devices of this type employ two stage refrigeration such that at the first stage of the refrigerator temperatures of between 35.degree. and 85.degree. Kelvin (K.) are achieved when helium is the working fluid and temperatures of 10.degree. to 20.degree. Kelvin are achieved at the second stage with the same working fluid.
U.S. Pat. No. 3,119,237 discloses a refrigerator of the type using a rotary valve which tends to promote leakage as the valve wears.
U.S. Pat. No. 3,205,668 shows a current two ported valve of the type employed with a pneumatically actuated refrigerator.
U.S. Pat. Nos. 3,625,015 and 3,312,072 show a single and dual rotary valve disk respectively.